Method of preparing light-colored paraffin sulfonic acid

ABSTRACT

A method of preparing a light-colored paraffin sulfonic acid comprising the steps of separating a heavy layer containing paraffin sulfonic acid from an reacted mixture obtained through sulfoxidation reaction of paraffin and concentrating said heavy layer, wherein the concentration of the heavy layer is carried out in the presence of hydrogen peroxide.

United States Patent Nagayama et a1.

[4 1 May 30, 1972 [54] METHOD OF PREPARING LIGHT- COLORED SULFONIC ACID[72] Inventors: Masuzo Nagayama, Tokyo; 'lerunosuke Kawana,Funabashi-shi, both of Japan [30] Foreign Application Priority Data Nov.20, 1968 Japan ..43/84770 [52] U.S. Cl. ..260/513 R [51] Int. Cl ..C07c143/02 [58] Field of Search ..260/513 R [56] References Cited UNITEDSTATES PATENTS 3,485,870 12/1969 Bost ..260/513 R 3,424,693 I/ 1969Stein et a]. ..260/513 R 3,372,188 3/1968 Alston et al ..260/513 RFOREIGN PATENTS OR APPLICATIONS 902,614 1/1954 Germany ..260/513 R1,052,484 12/ 1966 Great Britain ..260/513 R 65,919 3/1969 Germany..260/513 R Primary Examiner-Daniel D. Horwitz Attorney-Woodhams,Blanchard and Flynn [57] ABSTRACT A method of preparing a light-coloredparafiin sulfonic acid comprising the steps of separating a heavy layercontaining paraffin sulfonic acid from an reacted mixture obtainedthrough sulfoxidation reaction of paraffin and concentrating said heavylayer, wherein the concentration of the heavy layer is carried out inthe presence of hydrogen peroxide.

7 Claims, No Drawings METHOD OF PREPARING LIGHT-COLORED PARAFFINSULFONIC ACID BACKGROUND OF THE INVENTION 1. Field of the Invention Thepresent invention relates to an improved method of sulfoxidation whichis capable of producing a light-colored paraffin sulfonic acid. To beprecise, it relates to a method of preparing a parafi'rn sulfonic acidwhile preventing the coloring of the sulfoxidation reaction product inthe course of its purification.

2. Description of the prior art Paraffin sulfonic acid is obtained bycausing sulfur dioxide gas to react on n-parafiin or a branched paraffinhaving a carbon atom number in the range of in the presence of oxygenand at a temperature in the range of 0 80 C. As for said sulfoxidationreaction, the well-known methods include one employing gamma rays as thereaction initiator such as British Pat. No. 810,574, one employingultraviolet rays as said initiator such as Japanese Pat. No. 160,811,one employing a peroxide as the initiator such as Belgian Pat. No.445,312, one employing an azo compound as the initiator such as the U.S.Pat. No. 2,503,280, etc., and, in any of these methods, the reactionprogresses by the same mechanism. In case where the sulfoxidationreaction is effected with an anhydrous system, colored substancesattributable to a secondary reaction are apt to be coincidentallyproduced. There are instances where water is added as a means ofpreventing such secondary reaction. In case where said reaction iseffected in the presence of water, the reacted mixture itself may belightcolored, but inasmuch as such after-treatment as concentration isrequired for removing the by-product sulfuric acid, the desired endproduct tends to be colored. For instance, such a method as thelight-water process disclosed in Belgian Pat. No. 709,864 includes aconcentration step, but the end product obtained thereby is remarkablycolored.

The fact that sulfuric acid is produced as a by-product even in casewhere no water is employed may be evident from the reaction sequencedescribed below.

RH SO 60 RSO Ol-I (wherein R represents paraffin hydrocarbon radical.)

The sulfoxidation reaction of paraffin expressed by the foregoinggeneral reaction formula progresses in terms of radi- As seen even fromthe foregoing radical reaction formula, the product of sulfoxidationreaction usually contains sulfuric acid produced by the secondaryreaction, and the amount of said by-product sulfuric acid is in therange of about 54; niol per 1 mol of the sulfonic acid produced in casewhere the reaction system is maintained in a substantially anhydrousstate, whereas, in case of the state in which water is containedsufiiciently in the reaction system, sulfuric acid is produced as abyproduct in an amount equivalent to the sulfonic acid produced in termsof mols.

Meanwhile, the paraffin sulfonic acid obtained through the sulfoxidationreaction is often employed for various uses usually upon altering itinto the sulfonate. On the occasion of altering said sulfonic acid intosulfonate by means of neutralization, if there exists any sulfuric acid,said sulfuric acid also changes into a sulfate simultaneously. But, ingeneral, the existence of sulfate mixed with the sulfonate isundesirable, and particularly in case where paraffin sulfonate isutilized as the base of a light-duty liquid detergent, it is considereddesirable to have the least possible amount of sulfate mixed therein.

For such reason, the reaction mixture obtained through sulfoxidation,which contains paraffin sulfonic acid, has hitherto been subjected to atreatment for removing the by-product sulfuric acid existing therein.That is, according to the conventional method of removing the by-productsulfuric acid, the phase separation of the reaction mixture is efiectedby means of either adding water to the reaction system in advance oradding water to the reaction mixture resulting from sulfoxidation, andthen a heavy layer containing paraffin sulfonic acid is first separatedfrom the layer comprising the unreacted paraffin as the main constituentthereof. Subsequently, said heavy layer is either concentrated andthereafter, left standing, or further heated and thereafter leftstanding at a high temperature. This method is capable of removing morethan percent of the by-product sulfuric acid.

However, the paraffin sulfonic acid thus separated from the by-productsulfuric acid is remarkably colored as stated above, and, to make itworse,such coloring can hardly be lightened even by a bleachingtreatment.

SUMMARY OF THE INVENTION One object of the present invention is toprovide an improved method of preparing paraffin sulfonic acid whichcomprises the steps of separating a heavy layer containing paraffinsulfonic acid from the reaction mixture obtained through thesulfoxidation reaction of paraffin and concentrating the heavy layerthus separated, said concentration being effected by means of addinghydrogen peroxide to said heavy layer.

Another object of the present invention is to-provide a lightcoloredparaffin sulfonate suitable for use as the base of a light-duty liquiddetergent.

When the cause of the coloring of the paraffin sulfonic acid to beobtained through the conventional method is examined, the coloring isconsidered attributable to the treatment per se for removing theby-product sulfuric acid from the heavy layer in the light of the factthat an extremely light-colored heavy layer can be obtained according tothe conditions for reaction in said sulfoxidation. When the heavy layeris examined from this point of view, said layer is expected to containsulfinic acid, and it is considered that said sulfinic acid may giverise to a disproportionation reaction such as:

3RSO H RSO H RSO SR H O because of its instability, on the occasion ofthe heavy layer being concentrated or heated, and that the product fromsaid reaction becomes a portion or the main constituent of the coloringcomponent or the stench-generating component of the paraffin sulfonicacid due to further decomposition of said product and so forth.

The present invention has been proved successful in producing anextremely light-colored parafi'm sulfonic acid by means of previouslyadding an oxidizing agent for sulfinic acid to the heavy layer on theoccasion of removing the by-product sulfuric acid from said heavy layer.In other words, the method of preparing a paraffin sulfonic acidaccording to the present invention comprises the steps of addinghydrogen peroxide to the heavy layer separated from the reaction mixtureprepared by sulfoxidation of paraffin and said heavy layer isconcentrated in the presence of said hydrogen peroxide.

The unstable sulfinic acid contained in the heavylayer is stabilized asit is altered into sulfonic acid by virtue of hydrogen peroxide addedthereto, and the aforesaid product resulting from the decomposition ofthe product from a disproportionation reaction is coincidentallydecolored and deodorized through oxidation by said hydrogen peroxide.According to the present invention, therefore, it is possible to producea less fetid and light-colored paraffin sulfonic acid. And, in case of aparaffin sulfonic acid to be obtained through concentration in thepresence of hydrogen peroxide and giving out a complicated, offensivesmell accompanied by a smell like a low-grade carboxylic acid, saidsmell can be eliminated by means of steam distillation of said sulfonicacid under either acidic conditions or neutral conditions. It is to benoted that said steam distillation is conspicuously effective as a meansof deodorization.

According to the method under the present invention, the sulfoxidationreaction of paramn is not subjected to any particular limitation. As thematerial paraffin, therefore, any one of n-parafiins or branchedparaffins having a carbon atom number of 10-20 which are obtained fromthe kerosene fraction of petroleum and the like by the molecular sievemethod or the urea-adducting method is applicable. As to the conditionsfor reaction, too, any appropriate conditions may be used. For instance,there may be employed a reaction initiator such as described in theforegoing, a reaction accelerator, or water for the purpose ofcontrolling the secondary reactions.

The adding of hydrogen peroxide to the heavy layer may be carried out bydissolving said hydrogen peroxide in water or other appropriate solvent.However, the amount of hydrogen peroxide to be added is in the range of001-10 percent by weight of sulfonic acid contained in the heavy layer,and it is particularly advisable to be in the range of 0.1-5 wt percent.The temperature, the pressure and the period of time required for theadding of hydrogen peroxide are usually -l80 C, atmospheric pressure toseveral atmospheres pressure and min. to several hours, respectively,but are not necessarily limited thereto. Further, the state of the heavylayer at the time when hydrogen peroxide is added is suitable if it issuch that it will permit a thorough mixing with hydrogen peroxide, andit may be in the liquid state, slurry state or paste state. But, it isdesirable to expel sulfur dioxide gas existing in the heavy layer, priorto adding hydrogen peroxide thereto, by means of heating said layer at atemperature of more than 50 C.

According to the method under the present invention, the paraffinsulfonic acid can be separated from the by-product sulfuric acid,without causing any coloring of the former, through concentration of theheavy layer in the presence of hydrogen peroxide, but it is desirablethat hydrogen peroxide be contained in the heavy layer subsequent tosaid concentration. Therefore, hydrogen peroxide is further added to theheavy layer subsequent to concentration thereof and/or separation of theby-product sulfuric acid therefrom. The amount of hydrogen peroxide tobe added on this occasion is in the range of 0.01- wt percent, and thisadditional employment of hydrogen peroxide can be expected to be all themore effective for preventing coloring and for deodorizing the paraffinsulfonic acid concerned.

The crude paraffin sulfonic acid separated from the byproduct sulfuricacid may be subsequently subjected to such treatments as neutralizationand removal of unreacted oil, etc., but it goes without saying that thepresent invention is not intended for specifying these treating methodor the conditions thereof. Nevertheless, it is an indisputable factthat, in case where the paraffin sulfonic acid separated from thebyproduct sulfuric acid is subjected to steam distillation under thecondition of pH value being l.58, the paraffin sulfonate resultingtherefrom comes to be much less fetid.

DESCRIPTION OF THEPREF ERRED EMBODIMENTS Example 1 In a cylindricalreactor equipped with a lamp jacket for the purpose of internalirradiation was placed n-paraffin having a carbon atom number of 14-17,and sulfoxidation of said paraffin was carried out continuously at 25-30C by means of irradiation with a high-pressure mercury lamp whileblowing a mixture gas comprising sulfur dioxide gas and oxygen mixed atthe volume ratio of 2:1 into the reactor from its bottom, By addingwater continuously from the upper part of the reactor, the reactedmixture was extracted, whereby there was obtained a heavy layer havingthe following composition.

THE COIVIPOSITION OF HEAVY LA YER Sulfonic acid 17.1 wt% Sulfuric acid6.2 wt% Paraffin 12.9 wt% Water 63.8 wt% Thus obtained heavy layer wasput in a rotary evaporator, subjected to 20 min. concentration underreduced pressure at a bath temperature of C in the presence of theadditive such as shown in the following table, and thereafter the stateof coloring of the concentrated liquid was measured. The result of themeasurement was as shown in the same table. In this connection, theGardner color of said heavy layer prior to the concentration was 1.

THE STATE OF COLORING OF THE CONCENTRATE 2 ,G-di-tert-butyI-p-cresolExam le 2 The heavy layer obtained in Example 1 was subjected to 20 min.concentration under reduced pressure at 80 C, and subsequently theresultant concentrate was left standing while maintained at C. Theefficiency of hydrogen peroxide employed in the separation of sulfuricacid was as shown in the following table. In this connection, saidhydrogen peroxide was employed as a 30 percent aqueous solution thereof.

VARIATION OF THE GARDNER COLOR Amount of At the end of After Additionalhydrogen separation employment of peroxide concentration of sulfuric H0, (lwt%) added acid Example 3 The heavy layer obtained in Example 1 wasmaintained at 80 C, and subjected to concentration under reducedpressure by means of a rotary evaporator until the water content became10 percent by weight of said layer. The Gardner/color of thusconcentrated heavy layer was more than 18. The Gardner color of saidconcentrated heavy layer when it was neutralized with 40 percent causticsoda after separation of sulfuric acid therefrom was 11, and the Gardnercolor when hydrogen peroxide in the amount of 3.0 percent by weight ofsulfonate was added to thus neutralized heavy layer was 3.

On the other hand, in case where hydrogen peroxide in the amount of 3percent by weight of sulfonic acid was previously added to the heavylayer prior to the concentration under reduced pressure, the Gardnercolor of the concentrated heavy layer obtained after separation ofsulfuric acid decreased to 1. And, when this concentrated heavy layerwas neutralized with 40 percent caustic soda and then subjected to thesteam distillation eliminating the unreacted parafiin andstench-generating components, the Gardner color was 1. As a result, itwas possible to obtain a light-colored and less odorous parafiinsulfonate in the state of a paste.

What we claim is:

1. In a process of preparing sulfonic acids which comprises contactingparaffinic hydrocarbon with sulfur dioxide and oxygen in a sulfoxidationreaction to produce a heavy layer of an aqueous phase containingparafiin sulfonic acid, sulfuric acid, unreacted parafi'inic hydrocarbonand sulfur dioxide, separating said heavy layer from the remainder ofthe reaction mixture, and then concentrating said heavy layer to removesulfuric acid therefrom, the improvement which comprises adding to andmixing with said heavy layer, after it has been separated from theremainder of said reaction mixture and prior to said concentrating step,from 0.01 to percent by weight of hydrogen peroxide, based on the weightof parafi'm sulfonic acid in said heavy layer, so that the hydrogenperoxide is present during the concentrating step to minimize thefonnation of coloring and/or odor-iferous substances during theconcentrating step.

2. A process according to claim 1, in which water is added to thereaction mixture during the sulfoxidation reaction. I

3. A process according to claim 1, in which water is added to thereaction mixture after the sulfoxidation reaction is completed and priorto separation of the heavy layer.

4. A method according to claim 2, in which an additional amount ofhydrogen peroxide in an amount in the range of 0.0] 10 percent by weightbased on the sulfonic acid present in the heavy layer, is added to andmixed in the heavy layer after the concentrating step.

5. A method according to claim 2, in which the heavy layer, afterremoval of the sulfuric acid therefrom, is subjected to steamdistillation at a pH between 1.5 and 8.

6. A method according to claim 3, in which an additional amount ofhydrogen peroxide in an amount in the range of 0.01 10 percent by weightbased on the sulfonic acid present in the heavy layer, is added to andmixed in the heavy layer after the concentrating step.

7. A method according to claim 4, in which the heavy layer, afterremoval of the sulfuric acid therefrom, is subjected to steamdistillation at a pH between 1.5 and 8.

2. A process according to claim 1, in which water is added to thereaction mixture during the sulfoxidation reaction.
 3. A processaccording to claim 1, in which water is added to the reaction mixtureafter the sulfoxidation reaction is completed and prior to separation ofthe heavy layer.
 4. A method according to claim 2, in which anadditional amount of hydrogen peroxide in an amount in the range of0.01 * 10 percent by weight based on the sulfonic acid present in theheavy layer, is added to and mixed in the heavy layer after theconcentrating step.
 5. A method according to claim 2, in which the heavylayer, after removal of the sulfuric acid therefrom, is subjected tosteam distillation at a pH between 1.5 and
 8. 6. A method according toclaim 3, in which an additional amount of hydrogen peroxide in an amountin the range of 0.01 * 10 percent by weight, based on the sulfonic acidpresent in the heavy layer, is added to and mixed in the heavy layerafter the concentrating step.
 7. A method according to claim 4, in whichthe heavy layer, after removal of the sulfuric acid therefrom, issubjected to steam distillation at a pH between 1.5 and 8.